A late entry into a packed category of smartphones, Amazon's Fire phone offers a variety of unique features. Now, the reviewers are assessing whether they are enough to make the phone stand out.

Many of the reactions have similar themes: some great technology that could appeal to some buyers, but it's questionable whether this phone can become a hit in a marketplace full of excellent devices.

The Fire does sport several unique features. There's Dynamic Perspective, in which four tracking sensors on the front of the phone track a user's head, moving the perspective of the screen's generated imagery when the user's head moves. The effects produced include, for instance, being able to see the 3D sides of an icon as you move your head, or as you tilt the phone.

Fire's Firefly

After the "wow" impact fades, the question is whether Dynamic Perspective offers anything of value. Reviewers have noted that some apps allow for panning a still photo using this feature, without having to scroll with your fingers, or seeing additional information hidden behind places on a map.

The other big new feature is Firefly. "Firefly isn't a core smartphone feature like, say, maps or e-mail," said Andrew Cunningham in ArsTechnica. "It just feels like a thing that technology should be able to do."

Firefly does a lot of things, all of which relate to its ability to capture an image through the phone's camera and immediately give you more information about the pictured object -- including whether it's for sale at Amazon or other participating retailers. The database of recognized objects is growing, but reportedly already includes many kinds of packaged goods with recognizable logos, ranging from cereal boxes to books.

The technology can also listen to a song, a TV show or a movie, and place it within a context, especially if it's in Amazon's inventory. This is similar to other apps, except Firefly can identify exactly where in a TV episode the sound capture came from, and immediately convey information about every actor in that scene.

'Confusing' UI

The phone also has menus that can be swiped in from the sides, top and bottom, or, brought in hands-free by tilting the phone.

Avi Greengart, an analyst with industry research firm Current Analysis, told us that his reading of several reviews failed to turn up something he found -- that "the user interface can be confusing."

"It doesn't support multi-tasking," he noted, "so you have to go back to the home screen to jump between apps." Additionally, he said, if you accidentally nudge the device, or don't hold it the right way, a menu can pop up from the sides, top or bottom.

"This is fine if that's your intention," Greengart said. He recalled that he was reading a Web page on the phone, and it started scrolling automatically because he had apparently titled the phone a bit too much.